Definition - Paid search is the buying of keyword(s) from a search engine for the sponsored ads.

Marketing - This is typically one of the top paid marketing channels for introducing users/customers for online marketing. It’s typically used for top of the funnel marketing in terms of branding and exposure but can also help finalize a sale or lead for a user/customer.

Optimization -

It’s important to identify keywords that drive quality users to your site. This can be measured by time on site and conversion rate.
Once keywords are identified - utilize phrase matching and related keywords for additional traffic
Make sure to identify and remove negative keywords that have negative roi and zero conversions.